It's honestly kind of strange that the conventional wisdom is "you don't need types for one-off scripts"

I get the idea but just think about what your average shell script does. It usually runs through a list of commands, often taking several seconds, minutes or even hours, while setting up tons of imperative state on your system that is hard/annoying to undo. These are exactly the kinds of tasks that I want to go right on the first try, much more so than most larger systems even. Trying to restart a half-finished script that failed somewhere after half an hour, just because you messed up something simple is a terrible experience.